柴油机二次喷射燃烧系统流场分析

Numerical simulation of flow field in DI diesel engine with secondary injection by combustion chamber wall

以 KIVA3为计算平台 ,对 4气门直喷式非增压柴油机在油注喷向燃烧室侧壁后飞溅形成二次喷射燃烧的整个工作过程进行了模拟计算 ,着重分析了压缩和膨胀做功冲程缸内流场。得出以下结论 :在进气涡流作用下 ,活塞压缩后期产生的挤流以螺旋线路进入燃烧室 ,因此对若干几何参数一样的喷孔喷出的油注产生的柴油气的作用不同 ,进而各油注的燃烧历程也不同。对带有二次喷射导向壁面的小口径比和小径深比的ω型燃烧室 ,充分利用活塞顶面以上氧气的问题仍有待解决。

The combustion process in the 4-valve DI diesel engine with secondary injection by combustion chamber wall was simulated based on KIVA3. Analyzes the flow characteristics in compression and expansion strokes. The following conclusions are drew: affected by the intake swirl, squish forming at the later stage of compression stroke comes into combustion chamber along the screw-lines. The squish produces different forces on each spray that is formed in the same geometry nozzle holes. So the combustion process of each spray is different. The ω-combustion chamber with small caliber ratio, small surface-volume ratio and leading wall of secondary spray is not very well to make use of oxygen above piston surface and in the upper portion of combustion chamber.